The proposed research will determine the role of arachidonic acid and other prostaglandin precursors on the cardiovascular system of the dog. The corresponding endoperoxides will be synthesized and compared with the precursor acids and prostaglandins in the presence and absence of cyclo oxygenase inhibitors to determine whether the effects of the precursors are mediated through the observed vascular properties of the endoperoxides or the prostaglandins. The in vivo studies will be corroborated and extended with vascular strips; the role of arachidonic acid as a mediator of endogenous vasoactive substances will be studied by estimation of this acid, endoperoxide and prostaglandins. BIBLIOGRAPHIC REFERENCES: "Vascular Responses to the Monoenoic Prostaglandin (PG) Precursor Dihomo-gamma-Linolenic Acid (DGLA) in the Perfused Canine Lung", T.C. Wicks, P.W. Ramwell, J.C. Rose and P.A. Kot, Abstract, American Physiological Society, 1976. "Role of the Lung in Arterial Pressure Response to Arachidonic Acid in Dogs", H. Waldman, I. Alter, P. Kot, J. Rose, P. Ramwell and E. Ramey, Abstract, American Physiological Society, 1976.